Acoustic apparatus



Patented July 9, 1935 UNITED STATES PATENT OFFICE ACOUSTIC APPARATUS Application December 6, 1933, Serial No. 701,131

16 Claims.

This invention relates4 to acoustic apparatus. More particularly, it relates to the electrodynamic or moving coil type of acoustic apparatus in which the moving coil is divided into a plurality of windings adapted to be energized by different bands of frequencies within the audible spectrum.

In the copending applications of Abraham S. Ringel S. N. 661,237 filed March 17 1933 and Harry F. Olson S. N. 673,823 filed June 1, 1933, electrodynamic acoustic apparatus is disclosed in which the moving coil is divided into a plurality of sections adapted to be energized at different frequencies. When the moving coil is divided into only two sections, one section is adapted to be energized at high frequencies and the other section is adapted to be energized at low frequencies or, in some instances, one winding only is energized at high frequencies and both windings are energized at low frequencies. The two windings are arranged on the voice coil form with the high frequency winding adjacent the diaphragm and' the low frequency winding spaced therefrom by compliant coupling means. The coupling means is adjusted so as to be relatively flexible at high frequencies and relatively rigid at low frequencies. Leads from the low frequency winding extend over the compliant coupling to the high frequency section.

It is found that in some instances breakage occurs in the leads extending over the compliant coupling due to the relative movement between the high frequency winding and the low frequency winding. This is most noticeable when the connections cross the compliant coupling 35 either over it, under it or through slots cut in the coupling in a direction longitudinal of the coil form. This diiiiculty has been overcome to some extent as shown in the aforementioned Olson application, by arranging the connecting conductors so that they cross the compliant coupling at an angle thereto. However, this arrangement has not proved entirely satisfactory.

It is the object of this invention to provide conductors for supplying energy to the winding spaced from the diaphragm by the compliant coupling, which will not break when the two windings of the voice coil are vibrated relatively to each other, and which will function satisfactorily as electrical conductors as long as the remainder of the vibratile system remains in operative condition. This obj ect is attained by using conducting material for the compliant coupling and by dividing the compliant coupling into a plurality of longitudinally extending sections, electrically isolated or insulated from each other,

and by connecting the terminals of the winding spaced from the diaphragm by the compliant coupling to different sections of the coupling member and using each section as a conductor. The longitudinal sections of the conducting meinber are connected at other points to the circuit for energizing the winding.

The broad idea of the invention is also adaptable to other uses as will be set forth more clearly in the following specification and appended claims. More specific objects of the invention will also become apparent upon reading the specification and claims.

The invention is illustrated in one of its modifications in the accompanying drawing in which,

Fig. l is a cross sectional View of the vibratile system of an electrodynamic loudspeaker of the double voice coil type,

Fig. 2 is a detailed View illustrating how the invention is applied to the loudspeaker,

Fig. 3 is a sectional vieW on the line III- III of Fig. 2,

Fig. 3a is a sectional view of a modification of the device shown in Fig. 3.

Fig. 4 is a circuit illustrating an approved form of the connections for the voice coil windings of Fig. 2, and

Fig. 5 illustrates the manner in which the windings of Fig. 2 are connected to the source of energy.

Fig. 6 is a plan view of a modification of the coil form shown in Figs, 2 and 5.

In the apparatus illustrated by Fig. l the vibratile system of the loudspeaker is indicated generally at l0. It consists of the diaphragm l2 and the driving coil attached thereto. The diaphragm is frusto-conical in shape and is supported at both bases by suitable supporting members. The larger base of the diaphragm l2 is supported, for example, by means of an annular rim of flexible material I4 secured to a suitable supporting member I6. The smaller base of the diaphragm is supported by a spider member i8 in the manner well known in the art. The spider member I8 may either be secured to the inner pole piece 20 of the magnet system as shown in Fig. l or it may extend externally of the diaphragm and be secured to the outer pole piece 22. A coil form 24 having a voice coil 26 wound thereon is secured to the smaller base of the diaphragm. The coil form is secured to the diaphragm in such a manner that the voice coil 25 extends within the air gap between the central and outer pole pieces 20 and 22. When the coil 26 is energized with audio frequency variations the now of current through the coil causes movement thereof and consequently of the diaphragm i2 in the manner well known in the prior art.

ln accordance with the aforementioned Ringel and Olson inventions, the voice coil 25 is divided into two windings 2S and 39; These windings are separated from each other by a compliant coupling 32 formed in the coil form 2d. The compliant coupling is preferably formed by providing annular corrugations in the coil form. The winding @il comprises the high frequency winding of the voice coil and the winding 28 comprises the low frequency winding. Means are provided for energizing only the winding 35i at high frequencies and for energizing either the entire coil i. e., both the winding 28 and the winding 3&3, at low frequencies or else energizing only the winding g8 The compliant couplincr 32`V at low frequencies. is quasi-flexible, the degree of flexibility being relatively high at high frequencies and relatively low at low frequencies. rhus, at high frequencies the Winding 23 does not move to an appreciable extent due to the aforesaid connection ,between winding 28 and winding 35i and at low frequencies when the winding 2S is energized and lthe compliant coupling is comparatively rigid,

both windings move together asia unit. As a result of this arrangement the effective mass of the driving coil isv materially reduced at high frequencies due to the fact that there is substantially no vibration of the winding 2t and the section of the voice coil form on which it is wound.

In double voice coil loudspeakers of the type hereinbefore described, it is desirable to have the leads for supplyingV energy Vto the different windings extend' to the external circuit frorn'someV point between the diaphragm if. and the outer pole piece 22. In some instances it is desirable to have the vleads secured to the diaphragm l2 or to the coil form 2t, in the neighborhood of the junction between the diaphragm and the coil form. f

Some diiiiculty has been experienced due to eachother, and by connecting the terminals of the winding 23 to these sections. The ends of the sections adjacent the diaphragm are then connected in the circuit which supplies Venergy Lo the winding.

Figs. 2 and 3 illustrate an approved form of the invention.` The diaphragm 2 has a coil form secured thereto in the usual vmanner but in this instance the coil form is formed of conducting material andis divided by two longitudinal cuts or slots 3a into two semi-cylindrical sections and 33. The coil form has windings ZS and arranged thereon justas in the apparatus of Fig. l and it is provided with annular corrugations forming a compliant coupling 52 just as in the apparatus of Fig. l. One terminal of winding 2t is connected to the semi-cylindrical section 35 and the other terminal of the winding 28 is connected to the semi-cylindrical section 33. Suitable connections are made to the sections 35 and 3% at the ends thereof adjacent theirconnection with the diaphragm l2, for supplyingY energy to the winding 23.

When the entire coil form is composed of conducting material it is usually desirable to provide some sort of means for retaining the two semi-cylindrical portions in their relative positions. This may be accomplished by providing small cylindersk of non-conducting material adapted to t either inside or outside of the coil form. The semi-cylindrical sections may also be retained in place by placing the two sections on a suitable form, winding the windings 23 and 3Q about the sections and then applying lacquer or any other suitable substance to the windings and voice coil sections so as to unite winding 2S and its associated parts of sections 36 and 38, and winding il@ and its associated parts of sections St and 3S into two substantially rigid sections with the compliant coupling 32 interposed therebetween.; Thek lacquer or other cementing substance will have the. additional property of elec.- trically insulating the sections B and 33 from each other andfrom other parts of the system. It is especially desirable, for example, to have sections St and 38 sufficiently coated with insulating material so that they will not rub against either the inner or outer pole pieces 2% and 22 and thereby short circuit 'the winding 28. i

Figure. 3a is a cross sectional View illustrating how the insulating material may be applied'to 'the inner and outer surfaces of memberstand '33, and also in the spaces between the sections.

lt is not necessary to form the entire coil form of conducting material as the compliant coupling 32 may be made of a different material from that of the cylindrical coil form sections supporting windings 2S and 39. For example, windings 28 and 36 may each Ybe supported by a cylindrical member of paper or other suitable material and the members may be joined by a metallic compliant coupling member $2. The compliant coupling member may then be cut by longitudinal slots into two semi-cylindrical portions lindrical sections 36 and 3S, it is to be understood that the sections need not be semi-cy indrical but vmay be of anyV form or shape as long as two longitudinally extending conductors are forme-:1 thereby. For example, the slotsl might extend helically or diagonally along the coil form. Wore'.- over, in some instances such as where the voice coil is divided into three sections i. e., a high frequency section,an intermediatev section and a low frequency section, the coil Vform or ,compliant coupling is divided into sufficient sections to provand the diaphragm and it might alsobe desirable CII to respond to high frequencies. yhand low frequencies pass through both windresponding to that of Fig. 4.

to -securethevoice coil leads to the diaphragm.

iWith thisarrangement the voice coil form and the compliant coupling members are divided into i a number ofsections depending on the number -of `external leads that are required by the specific circuit arrangements used to supply energy to the windings.

-Fig. 4 illustrates one of the circuit arrangements for energizing the windings 28 and 30.

fAccording tothis circuit arrangement windings 28 and 30 are connected in series and winding In this arrangement high thus causing winding 38 to be the only winding On the other ings and cause both windings to respond thereto.

vIt will be seen that a point 42 is connected to one terminal on winding 28 and one terminal on winding 30. The windings are supplied with enlergy from any source such as the output of a -radio receiver.

The energy is supplied at the two terminals marked Input in Fig. 4.

Fig. vshows how the terminals of windings 28 and 38 are connected to the sections 35 and 38 when the windings are connected in a circuitl cor- The leads for supplying energy from an external source are indicated at 44. The leads are secured by any suitable means such as staples 46 to the diaphragm l2.

One of the leads 44 is Vconnected at 48 to one terminal of the high frequency winding 38 and the other lead is connected as at 5D to section 36 of` the coil form. 'I'he other terminal of winding 30 is connected as at 52 to section 38 of the coil form. The terminals of coil 28 are connected respectively to sections 36 and 38 of the coil form, one terminal being connected to 35 as indicated at 54 and the other section being connected to section 38 as indicated at 56.

The flow of current through the two windings 28 and 3S is asfollows: from the source of audiofrequency through one of the leads 44 to pointV 58; throughl the conductive coil form section 3G to `point 54; through the low frequency winding 28 to point 56 on the conductive coil form 38; through the conductive coil form section 38 to point 52; through the lowfrequency winding 38 to point 48; and back through the other lead 44.

'The conductive section 38 and the two terminals 52 and 56 correspond to point 42 in the circuit of Fig. 4.

VIt is to be understood that thewindings 28 and 38 need not be connected in the exact manner shown in Fig. 4 but that they may be connected in anyk other suitable circuit arrangement such, for example, as any of those shown in the aforementioned Ringel and Olson applications.

Although no connections are shown in Fig. 5 for connecting the condenser 40 across the low frequency winding 28, it is obvious that the condenser may be connected in the circuit merely 4by connecting its terminals to the conductive coil form sections 36 and 38. Moreover, in some instances it is not necessary to connect a condenser across these two sections as the cuts 34 may be made of such a size that the two sections 36 and 38 constitute the two plates ofthe condenser havingr the desired capacity. In general, howeverjit is more desirable to connect a condenser 'across the coil form sections 36 and 38 and to make` the cuts 34 sufficiently wide so that the capacitive effect between the two sections is negligible. It is also possible to use the capacitive effect between sections 36 .and 38 and the pole pieces 20 and 22.

yIt is to be understood that the apparatus specifically described and illustrated herein is only one modification of apparatus embodying the invention and that various other modications and arrangements may be made without departing from the spirit of the invention which is to be limited only by the scope of the appended claims.

What I claim is: 1. A vibratile system for electrodynamic acoustic apparatus comprising a voice coil consisting of a pair of windings, a coil form on which the windings are disposed, a compliant coupling in said coil form separating the portions thereof on which said windings are disposed, said compliant couplings being formed of conducting material and divided into sections, and electrical connections between said sections and the terminals of one of said windings whereby said sections constitute leads for supplying energy to the windlng.

2. Electro-dynamic acoustic apparatus comprising a diaphragm, a voice coil for actuating said diaphragm, a coil form on which said voice coil is disposed, said voice coil being divided into a plurality of windings, compliant coupling means dividing said coil form into sections corresponding in number to the number of said windings, said compliant coupling means being of conducting material and divided into sections electrically insulated from each other, and connections from the terminals of certain of said windings to sections of said compliant coupling means whereby the sections constitute conductors for supplying energy to said windings.

3; Electrodynamic acoustic apparatus comprising a diaphragm, a coil form connected to said diaphragm, compliant coupling means dividing said coil form into portions, said compliant coupling means being separated into sections, a voice coil winding disposed on each of the coil form portions, conductive connections for supplying energy to eachr of the windings, and means for .completing the conductive connections to certain of said windings through sections of said compliant coupling means.

4'. Electrodynamic acoustic apparatus comprising a diaphragm, a voice coil form secured thereto, a compliant coupling dividing said voice coil form into a pair` of cylindrical sections, said couplingl being of conducting material and separated into a pair of sections electrically insulated from each other, a high frequency voice coil winding on the section of said voice coil form adjacent the diaphragm, a low frequency winding on the section of saidvoice coil form spaced from said diaphragm by the high frequency section and the compliant. coupling, and connections between the terminals of said low frequency voice coil and the sections of said compliant coupling, whereby said compliant coupling constitutes conducting means for supplying energy to said low frequency wind- 6. Electrodynamic acoustic apparatus compris- 'l ing a diaphragm, a voice coil form secured thereto, said Voice coil form comprising a cylindrical metallic memberdivided longitudinally into two parts electrically isolated from each other, compliant means extending circumferentially about said voice coil form to divide said yform into two cylindrical sectionsV one adjacent said diaphragm and the other spaced therefrom, a voice coil winding on each of said cylindrical sections, connections between the terminals of the Vvoice coil winding on the section spaced from' the diaphragm and the sections ofsaid voice coil form electrically isolated from each other whereby said sections comprise conductors for supplyingV energy to said winding, a second connection to one of said sections from an extern-a1 circuit, a second connection to the other section from one of the terminals of the winding on the cylindrical section of the voice coil form adjacent the dia- ,each other and vconnected respectively to the terminals of said winding.

8. Electrodynamic acoustic apparatus comprising a diaphragm, a coil form secured to said diaphragm, a compli-ant coupling dividing said form into two parts, a winding on each part, and conductorsimbedded in said coil form and extending from one side of said coupling to the other,

and electrical connections between said conductors andthe terminals of one of said windings.

9. A Vibratile system for electrodynamic acoustic apparatus comprising a voice coil consisting of a plurality of windings, a coil form on which the windings are disposed, compliant coupling means in saidY coil form separating the portions thereof on which said windings are disposed, said compliant coupling means including electrical conducting material and being divided into sections connected to the terminals of certain of said windings to function asl leads for supplying energy thereto.

y 10. Electrodynamic acoustic apparatus comprising a diaphragm, a 'voice coil for actuating said diaphragm, a coil form on Vwhich said voice coil is disposed, said voice coil being divided into a plurality of windings, compliant coupling means dividing said coil form into sections corresponding in number to the number of said windings, said compliant coupling means including aV layer of conducting material divided into sections electrically insulated from each other, and connections from the terminals of certain of said windings to the sections of said layer of conductv ing material whereby said sections constitute conductors for supplying energy to saidwindings.

1l. Electrodynamic acoustic apparatus comprising av diaphragm, a coil form Vconnected to said diaphragm, compliant coupling means dividing said coil form into sections, a voice coil winding disposed on each of said Sections, means forming a plurality of electrical conductive paths through said compliant coupling means, conductive connections for supplying energy to each of said sections, the conductive connections to certain of said windings being completed through the conductive paths through said compliant coupling means.

l2. Electrodynamic apparatus comprising a diaphragm, ra voice coil form secured thereto, a compliant Ycoupling dividing said voice coil form into a pair of sections one adjacent the diaphragm and the other spacedtherefrom by the coupling, said coil form and coupling including a layer of conducting material divided into a` pair of longitudinal sections electrically insulated fr'om each other, a high frequency voice coil winding on the section of said Voice coil form adjacent the diaphragm, a; low frequency winding on the section of said Voice coil form spaced from the diaphragm, and connections between the terminals of said low frequency voice coil and the conducting layer of the sections of said compliant'coupling for supplying energy to said low frequency winding. 1

13. Acoustic apparatus comprising a dia phragm, a voice coil winding for actuating said diaphragm, a voice coil form securedto said dia- Y pluagm and having saidfwinding arranged thereon, said voice coil form including two conductive members insulated from each other and extend-` ing longitudinally of the coil form, a compliant coupling in said coil form between said Awinding and said diaphragm, connections from-the terminals of said winding to said conductive members, and connections for supplying energy from an external circuit to bers. Y Y

14. Electrodynamic acoustic apparatus comprising a diaphragm, a coil form secured to said diaphragm, said coil form consisting of a'pair of longitudnial extending conductive members, a pair of windings on said coil form, connections between the terminals of one of said windings and said conductiveV members, means for preventing' short circuiting of said conductive members, and a lead from at least one of said conductive members to anexternalcircuit.

l5; Anfelectrodynamic loudspeaker comprising a diaphragm, a voice coil form secured to said diaphragm, said voice coil form comprising two semi-cylindrical members of conducting material electrically separated from each othena compliant coupling rcircumferentially dividing said coil form into two sections, a Voice coil winding on each-section, connections between terminals of one of said Voice coil windings and said semicylindrical members, and otherv connections to said semi-cylindrical members for supplying energy thereto to energize said voice coil. Y

16. Electrodynamic acoustic apparatus comprising a diaphragm, a voice coil form secured thereto, said voice coil form comprisingY a lcy-` lindrical metallic member divided longitudinally into parts electrically isolated from each other, compliant means extending Vcircumferentially about said voice coil form to divide said form into cylindrical sections, a voice coil winding on each of said cylindrical sections, connections between the terminals of at leastone of the Voice coil windings and sections Vof saidV Voice ycoil form electrically isolated from each other whereby said sections comprise conductors forsupplying energy to said winding, a secondconnection to one of said sections from an external circuit, and other connections between said windings and said sections for completing the circuits for supplying energy to said windings.

' LESLIE J ANDERSON said conductive mem- 

